This proposal concerns prospective, longitudinal investigation of the psychophysiological functioning (specifically, electrodermal activity) of children at risk for psychopathology by virtue of parental psychiatric illness. Accumulating evidence suggests that psychiatrically ill populations, especially schizophrenics, show characteristics and abnormal electrodermal activity. Moreover, some work indicates that unusual electrodermal response patterns, especially very fast skin conductance response recovery, may precede the onset of the illness. The proposed study would examine electrodermal activity in a population at risk for schizophrenia. It would focus on those aspects of electrodermal activity that have shown most promise as distinguishing psychiatrically ill from control samples. Especially of interest are the shape of the skin potential response and recovery rate of the skin conductance response when stimulus signal value is both low and high; bilateral differences in electrodermal activity, especially in those individuals who are unresponsive to stimuli; as well as the parameters of electrodermal latency, rise time, amplitude and frequency. Electrodermal data collected for this project will be compared with data collected previously on the same children so that important developmental trends can be determined. These data will also be compared with concurrent measures of social and psychological functioning, evaluated in the larger project. Predictions will be made about vulnerability to future pathology as well as resistance to maladjustment; these predictions will be tested in future research. The subjects in this study will be 98 children of schizophrenics, 41 children of manic-depressives, 59 children of physically ill, and 114 children of psychiatrically normal parents. The age range is 7-23 years. The direction of this research is towards prediction of vulnerability to psychopathology by means of understanding antecedents to mental illness and developing these into theoretical models. The long-term goal is prevention of mental illness, and if outcomes are positive, the present research should contribute towards development of early screening procedures.